1. Field of the Invention
The present invention relates to an image display device, and more particularly, to an image display device that can change the direction of an image, for example, rotate the image displayed on a display screen.
2. Description of the Related Art
Conventionally, a certain image display device is known to control the direction of an image displayed on its display screen such that the bottom of the displayed image is positioned at a vertically lower position of the display screen even if the display screen is rotated.
JP-2003-60940-A and JP-2003-274366-A each describe an electronic camera for controlling the direction of an image displayed on a display screen.
The electronic camera detects the posture of the electronic camera by a camera posture detector. The electronic camera records the detected posture together with an image captured by the electronic camera. Upon reproduction of the recorded image on a display screen, the electronic camera controls the direction of the image displayed on the display screen based on the detected posture that is recorded together with the image. A gravity sensor is used as the camera posture detector (see JP-2003-274366-A).
JP-H9-37187-A describes an image display device that rotates an image displayed on its display screen.
This image display device detects the posture of a user who is watching an image displayed on the image display device, instead of the posture of the image display device itself, by an infrared sensor. The image display device rotates the image displayed on the display screen by 90° when the user is sprawling. The infrared sensor senses a region in front of the display screen.
Japanese Patent No. 3013808 describes techniques for scaling up and down an image represented by an image signal.
When a gravity sensor detects the posture of an image display device as described in JP-2003-60940-A and JP-2003-274366-A, the following problems can arise.
When an image display device is installed such that its display screen is substantially horizontal to the ground surface, the result that is detected by the gravity sensor doesn't indicate the position of the user who is viewing the display screen. Therefore, the gravity sensor cannot always correctly detect the position of the user who is viewing the display screen. Accordingly, when the image display device is installed such that the display screen is substantially horizontal to the ground surface, the image display device cannot rotate a displayed image so that the user can easily watch the displayed image.
In addition, the gravity sensor cannot detect the posture of the image display device in a weightless environment such as a space station.
The image display device described in JP-H9-37187-A can arise the following problems, because the infrared sensor that is included in the image display device has a detectable region in front of the display screen.
When the image display device is installed such that the display screen is substantially horizontal to the ground surface, and when the user is watching an image displayed thereon at a position out of the front of the displayed image, the infrared sensor cannot always correctly detect the position of the user who is watching the displayed image.
FIG. 1 is an explanatory diagram illustrating an exemplary situation in which image display device 101 is installed such that display screen 102 of image display device 101 is substantially horizontal to the ground surface, and when user 201 is viewing display screen 102 at a position out of the front of display screen 102 (specifically at a position beside display screen 102).
Infrared sensor 103 has a detectable region in front of display screen 102. Therefore, in the state illustrated in FIG. 1, infrared sensor 103 cannot detect user 201. Consequently, image display device 101 cannot control the direction of an image such that the user 201 can easily watch the displayed image.